The famine was caused by a fungal disease called potato blight, which came to Ireland from Mexico. Blight made the potatoes quickly rot, and since a third to one-half of peasants were dependent on the crop for food, this led to more than 750,000 deaths.

But the famine was also the result of the social and political system in the 1840s. As Irish Catholics could not own land or hold a profession, the peasants resorted to growing mostly potatoes – which could be grown in large quantities on plots of rented land – to feed their families.